Several attributes of the cardiovascular system, including blood pressure (BP) and heart rate (HR), are characterized by predictable changes during the 24 hours for the most part in synchrony with the rest-activity cycle. During the past two decades specific features of the 24-hour BP pattern have been assessed as potential sources of injury to target tissues and as triggers of cardiac and cerebrovascular events in hypertensive patients. A growing number of studies indicate the reduction of the normal 10 to 20% sleep-time BP decline (non-dipper pattern) is associated with elevated risk of end-organ injury, particularly to the heart (left ventricular hypertrophy and myocardial infarct), brain (stoke) and kidney (albuminuria and progression to end-stage renal failure). Accordingly, there is growing interest in how to tailor the treatment of hypertensive patients according to their circadian BP pattern.
Clinical studies demonstrated a different effect of the ACEIs benazepril, enalapril, perindopril, quinapril, spirapril, and trandolapril when dosed in the morning versus the evening. A small trial on 33 patients with essential hypertension showed that a low dose of 2.5 mg/day ramipril more effectively reduced daytime BP when it was administered in the morning and more effectively reduced nighttime BP when it was administered in the evening. In the HOPE (Heart Outcomes Prevention Evaluation) study patients in the active treatment group received ramipril at bedtime. Results from a small substudy, in which hypertensive patients were evaluated with 24-hour ambulatory BP monitoring (ABPM), showed a marked BP reduction particularly during nighttime sleep, thereby reducing the prevalence of non-dippers. The authors concluded that the effects on cardiovascular morbidity and mortality seen with ramipril in the HOPE study may relate to its improved effect (i.e., increase in the diurnal/nocturnal BP ratio) on the non-dipping BP patterns.
In keeping with the documented administration-time dependent effects on BP regulation of other ACEI, this prospective chronotherapy trial will investigate the potential differing efficacy of ramipril in doses from 5 to 10 mg/day when administered, as a monotherapy either upon awakening from nighttime sleep or at bedtime, to diurnally active patients with grade 1 or 2 essential hypertension, who will be evaluated by 48-hour ABPM before and after pharmacologic intervention. The benefits from this trial may be extremely important, taking into account 1) the high prevalence of non-dipping among patients with essential hypertension, 2) the need for a proper 24-hour BP control with particular emphasis on the regulation of nighttime resting BP mean, and 3) the lacking information on the administration-time dependent effects on BP of ramipril, a widely used ACEI in doses of 5-10 mg/day.